Basement rock fractured formation mixed drilling well completion process

Abstract

The invention discloses a basement rock fractured formation mixed drilling well completion process. The process comprises the following process steps of: (1) drilling at a certain depth from an upper part loose layer to a basement rock layer by a mud positive circulation process, inserting a surface casing after the drilling, and fixedly sealing by using cement; (2) drilling the basement rock layer by an air downhole hammer reverse circulation process; (3) after a water-bearing layer is drilled, drilling convertibly by a gas lift reverse circulation process until a target layer is reached when drilling efficiency is influenced by back pressure, which is generated by a water column in a hole, on the downhole hammer; (4) washing a well by acidification; (5) washing the well by using a piston; (6) washing the well by using air; and (7) pumping water by using a water pump to complete the well, namely putting a submersible pump down to pump the water after the process that the well is washed by the air is finished until a water pumping test is finished. The invention has the advantages that: 1, dry holes are avoided or reduced, and construction risks are reduced; 2, a well constructioncycle is shortened, unnecessary investment is reduced, and production cost is reduced; 3, mud is not used, fresh water resources are saved, and environment pollution caused by mud construction or emission is prevented; and 4, all fractures are changed into water catchment channels to the maximum extent to realize the maximum water yield of a single hole.

Description

technical field [0001] The invention relates to a drilling process, in particular to a well-forming process of mixed drilling in a bedrock fissure stratum. Background technique [0002] The lithology of aquifers in bedrock fissures is dominated by intrusive rocks, volcanic rocks and volcanic lava, and groundwater exists in the fractured fracture zones developed by joints, structural fissures, weathering fissures and tension fissures. Generally, the width of the crack is 2 to 3 mm, the larger is 10 to 20 mm, and the length is several meters to more than ten meters. The groundwater is relatively enriched in the north-south, north-west tension or tension-torsion cracks, mainly diving, and the fractured zone. There is local vein-like confined water. The water richness is uneven and the water volume is poor. The spring water flow is generally 0.008 to 0.4 liters per second, the water output of the private well is 3 to 12 tons per day, and the water inflow per drilling hole is 3 ...

AI Technical Summary

Problems solved by technology

Due to the long drilling cycle of the conventional technology, the drilling cuttings, mud cake and fillings are not easy to wash out after the well is completed, resulting in a small water output from a single hole or dry holes without water, which makes drilling meaningless

In order to avoid the result of low water output or no water caused by blockage, it is currently a good idea to study a mixed drilling process in bedrock fractured formations that avoids artificial plugging of fractures and at the same time increases the permeability of fractures as much as possible. technical issues to be resolved